1. Field of the Invention
This invention relates to a method and apparatus for verifying and correcting the definition of the configuration of a link-connected network, especially an input/output (I/O) network in which host processors are coupled to peripheral device control units via switches and duplex serial fiber optic links.
2. Description of the Related Art
Input/output (I/O) systems for interconnecting processors and control units via serial fiber optic links have been previously described in the copending applications of P. J. Brown et al., Ser. No. 07/429,267, filed Oct. 30, 1989, U.S. Pat. No. 5,107,489 issued Apr. 21, 1992 for SWITCH AND ITS PROTOCOL FOR MAKING DYNAMIC CONNECTIONS, of M. C. Cox et al., Ser. No. 07/964,571 filed Oct. 21, 1992, a continuation of Ser. No. 07/444,190, filed Nov. 28, 1989, now abandoned and of A. Carusone et al., Ser. No. 07/516,387, filed Apr. 30, 1990, U.S. Pat. No. 5,167,667 issued Oct. 20, 1992 for METHODS AND APPARATUS FOR PERFORMING FAULT ISOLATION AND FAILURE ANALYSIS IN LINK-CONNECTED SYSTEMS, all of which are assigned to the owner of this application. In the system described in these applications, one or more crosspoint switches having serial fiber optic ports may be actuated to form either a static or a dynamic connection between pairs of ports to establish bidirectional communication between a processor and a control unit coupled to one or more peripheral devices such as a terminal, a printer, a direct access storage device (DASD) (e.g., a magnetic or optical disk drive), or a magnetic tape drive. In a typical installation, a first link may interconnect a processor and a switch, while a second link may interconnect the switch and a control unit to complete the connection between the processor and the control unit Each link may be several kilometers in length.
Planning and implementing the I/O configuration of a system such as the one described above can be a difficult and challenging task for the user There are two basic steps in enabling an I/O configuration: (1) the construction of a logical definition of the computing complex; and (2) the physical installation of I/O units and the cabling that interconnects these devices. Individually, each activity can be extremely complex. For example, in defining the logical I/O configuration the user must account for competing requirements and constraints when designing a plan for I/O accessibility.
Accuracy and consistency between the logical and physical I/O configuration is central to the ability to perform the full range of I/O operations, configuration management, and connectivity management which is required within the computer complex. Because of the complexity, the logical and physical I/O configurations may not match accurately. Mismatches between the two may indicate errors in the I/O configuration definition, mistakes made when the I/O units were cabled, or uninstalled or not operational I/O units. Where the mismatches result in gross errors, I/O operations may fail outright. Sometimes, these mismatches may not result in the inability to perform I/O operations and errors, but subtle problems, such as access to the incorrect I/O units, may not be detected. In other cases, I/O may be performed completely correctly, but the logical-to-physical differences can result in a degradation of configuration or connectivity management services.